GFCI that cannot be reset until wired correctly on line side and power is applied

ABSTRACT

A method and apparatus for a protection device for indicating when ground fault protection is not being provided by the protection device. The protection device includes source and load terminals between a conductive path and face terminals. The protection device further includes a latching mechanism, adapted to be operable between a first state in which the latching mechanism permits electrical contact between the source terminals and the load terminals and a second state in which the contact is broken; an alarm indicator, adapted to provide an indication that the protection device is not providing ground fault protection; and a fuse, adapted to blow when the latching mechanism fails to open during a manual test of the protection device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-In-Part of U.S. patent applicationSer. No. 10/434,101 filed on May 9, 2003 entitled “GFCI THAT CANNOT BERESET UNTIL WIRED CORRECTLY ON LINE SIDE AND POWER IS APPLIED”, theentire contents of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to ground fault circuitinterrupter (GFCI) devices. More particularly, the invention relates toa GFCI device that isolates the face terminals from the load side andprevents an initial miswiring of the GFCI from the load side.

BACKGROUND OF THE INVENTION

GFCI devices are designed to trip in response to the detection of aground fault condition at an AC load. Generally, the ground faultcondition results when a person comes into contact with the line side ofthe AC load and an earth ground at the same time, which is a situationthat can result in serious injury. The GFCI device detects thiscondition by using a sensing transformer to detect an imbalance betweenthe currents flowing in the line and neutral conductors of the ACsupply, as will occur when some of the current on the line side is beingdiverted to ground. When such an imbalance is detected, a solenoidactivates a latched circuit breaker within the GFCI device to an opencondition, thereby opening both sides of the AC line and removing allpower from the load.

Some GFCIs include a lockout feature that prevents the GFCI fromoperating if the solenoid fails to operate. For example, in U.S. Pat.No. 6,381,112 to DiSalvo, which is incorporated by reference herein, aGFCI is provided with a permanent lockout feature which prevents theGFCI from being reset if the solenoid fails to operate or if an openneutral condition exists. However, having a permanent lockout, whichprevents the GFCI from operating, can be undesirable. For example, if ahomeowner is entertaining guests in the kitchen, a power interrupt canoccur requiring the GFCIs to be reset. If a GFCI connected to anappliance is locked out, the homeowner may have to use an extension cordto connect an appliance to a non-GFCI receptacle. In front of guests,this can prove to be embarrassing and inconvenient to the homeowner.

GFCIs can also include an LED to provide a trip indication as disclosedin U.S. Pat. No. 4,568,997, to Bienwald et al., the contents of whichare incorporated herein by reference herein, This type of receptacleincludes test and reset pushbuttons and a lamp or light-emitting diode(LED) which indicates that the circuit is operating normally. When aground fault occurs in the protected circuit, or when the test button isdepressed, the GFCI device trips and an internal circuit breaker opensboth sides of the AC line. The tripping of the circuit breaker causesthe reset button to pop out and the LED to be extinguished, providing avisual indication that a ground fault has occurred. In order to resetthe GFCI device, the reset button is depressed in order to close andlatch the circuit breaker, and this also causes the LED to illuminateonce again. However, the GFCI disclosed in the Bienwald et al. patentdoes not provide an indication of a defective solenoid.

In addition to ground fault detection/protection, protection for thereceptacle terminals of the GFCI is also needed. Specifically, theconventional GFCI device has a set of load terminals that are sharedwith the receptacle terminals leading to the face of the GFCI.Typically, the AC source is connected to the line terminals while thedownstream load devices are connected to the load terminals. However, ifthe GFCI is miswired, this poses a problem. When the load terminals areconnected to an AC source, the receptacle terminals are powered. Theinstaller would be under the impression that the GFCI was operatingcorrectly. However, the installer would be unaware that the GFCI is notproviding ground fault protection even when a fault condition isdetected. Thus, while tripping the latching mechanism in response to amiswiring condition, only the downstream devices are open. Devicesplugged into the GFCI receptacle are still connected to AC power sincethe face terminals are directly connected to the line/load terminals.

It is therefore desirable to provide a latching mechanism that does notshare the contacts between the receptacle terminals and the loadterminals.

It is also desirable to provide a protection device that is notpermanently disabled when the solenoid fails.

It is also desirable to provide a protection device that providesprotection from miswiring, and permanently disables a miswiringprevention device once the protection device is correctly wired.

SUMMARY OF THE INVENTION

The above and other objectives are substantially achieved by a systemand method employing a ground fault circuit interrupter (GFCI) inaccordance with the principles of the present invention.

According to an embodiment of the present invention, a method andapparatus for a protection device for indicating when ground faultprotection is not being provided by the protection device is employed.The protection device includes source and load terminals between aconductive path and face terminals. The protection device furtherincludes a latching mechanism, adapted to be operable between a firststate in which the latching mechanism permits electrical contact betweenthe source terminals and the load terminals and a second state in whichthe contact is broken; an alarm indicator, adapted to provide anindication that the protection device is not providing ground faultprotection; and a fuse, adapted to blow when the latching mechanismfails to open during a manual test of the protection device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an example of a ground fault circuitinterrupting (GFCI) device in accordance with an embodiment of thepresent invention;

FIG. 2 is another perspective view of the ground fault interruptingdevice shown in FIG. 1 in accordance with an embodiment of the presentinvention;

FIG. 3 is a perspective view of an example of the ground fault circuitinterrupting device shown in FIG. 1 having an indicator in accordancewith an embodiment of the present invention;

FIG. 4 is a schematic diagram illustrating an example of the circuitryof the ground fault circuit interrupting device of FIG. 1 in accordancewith an embodiment of the present invention;

FIGS. 5–7 are perspective views illustrating examples of positions of alocking plate of the ground fault circuit interrupting device shown inFIG. 1 in accordance with an embodiment of the present invention;

FIGS. 8–10 are cross sectional views illustrating examples of positionsof the locking plate, a latching plate and a reset pin of the groundfault circuit interrupting device of FIG. 1 in accordance with anembodiment of the present invention;

FIG. 11A is a schematic diagram illustrating an example of the circuitryof ground fault circuit interrupting device of FIG. 3 in accordance withan embodiment of the present invention;

FIG. 11B is a schematic diagram illustrating an example of amodification of the circuitry of the ground fault circuit interruptingdevice of FIG. 11A in accordance with an embodiment of the presentinvention;

FIG. 11C is a schematic diagram illustrating another example of amodification of the circuitry of the ground fault circuit interruptingdevice of FIG. 11A in accordance with an embodiment of the presentinvention;

FIG. 12 is a schematic diagram of an example of a ground fault circuitinterrupting (GFCI) device in accordance with another embodiment of thepresent invention;

FIG. 13–16 are views illustrating examples of positions of a lockingplate in the GFCI of FIG. 12 in accordance with an embodiment of thepresent invention;

FIGS. 17A and 17B are cross sectional views illustrating examples ofpositions of a initial reset prevention arrangement that can be usedwith a GFCI in accordance with an embodiment of the present invention;and

FIGS. 18A and 18B are cross sectional views illustrating examples ofpositions of a another initial reset prevention arrangement that can beused with a GFCI in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a perspective view of an example of a ground fault circuitinterrupting (GFCI) device 10 in accordance with an embodiment of thepresent invention. The GFCI device 10 comprises a housing 12 having acover portion 14 and a rear portion 16. The GFCI also includes an innerhousing 13 (See FIG. 5) when the cover portion 14 is removed from therear portion 16. The cover portion 14 and rear portion are removablysecured to each other via fastening means such as clips, screws,brackets, tabs and the like. The cover portion includes plugin slots(also known as face receptacles) 18 and 20 and grounding slots 22. Itwill be appreciated by those skilled in the art that plugin slots 18 and20 and grounding slots 22 can accommodate polarized, non-polarized,grounded or non-grounded blades of a male plug. The male plug can be atwo wire or three wire plug without departing from the scope of thepresent invention. The GFCI receptacle 10 further includes mountingstrap 24 having mounting holes 26 for mounting the GFCI receptacle 10 toa junction box (not shown). At the rear wall of the housing 12 is agrounding screw 28 for connecting a ground conductor (not shown).

A test button 30 extends through opening 32 in the cover portion 14 ofthe housing 12. The test button is used to activate a test operation,that tests the operation of the circuit interrupting portion disposed inthe GFCI receptacle 10. The circuit interrupting portion, to bedescribed in more detail below, is used to break electrical continuityin one or conductive paths between the line and load side of the GFCIreceptacle 10. A reset button 34 extends through opening 36 in the coverportion 14 of the housing 12. The reset button 34 is used to activate areset operation, which reestablishes electrical continuity in the openconductive paths.

Rear portion 16 has four screws, only two of which are shown in FIG. 1.Load terminal screw 38 is connected to a neutral conductor and anopposing load terminal screw 37 (See FIG. 2) is connected to the hotconductor. Line terminal screw 40 is connected to the neutral conductorand an opposing line terminal screw 39 (See FIG. 2) is connected to thehot conductor. It will be appreciated by those skilled in the art thatthe GFCI receptacle 10 can also include apertures proximate the line andload terminal screws 37, 38, 39 and 40 to receive the bare end ofconductors rather than connecting the bare end of the wires to the lineand load terminal screws.

In an embodiment of the present invention rear portion 16 also containsan aperture 42 (See FIG. 2) for accessing the internal portion of theGFCI receptacle 10 for testing during the manufacturing process.Specifically, the aperture 42 provides access to a locking plate 58. Theaperture 42 is sealed prior to shipping of the GFCI receptacle 10 todistributors.

FIG. 3 is a perspective view of an example of a ground fault circuitinterrupting (GFCI) device 11 having an indicator in accordance with anembodiment of the present invention. Specifically, GFCI device 11 issimilar in operation to the GFCI 10 except GFCI device 11 has an alarmindicator 44 for providing an indication to a user that GFCI device 11is not providing ground fault protection, or in other words, GFCI device11 is operating as a normal receptacle.

Alarm indicator 44 comprises a dual color lamp which provides a firstcolor when a first filament is activated and a second color when asecond filament is activated. In an embodiment of the present invention,the alarm indicator 44 illuminates to provide a green color when theGFCI receptacle 11 is operating normally and providing GFCI protection.In another embodiment of the present invention, the alarm indicator 44illuminates to provide a flashing red color when the GFCI receptacle 11is operating as a normal receptacle and not providing ground faultprotection. It should be appreciated by those skilled in the art thatalthough the alarm indicator is described as being a dual filament lamp,two separate single filament lamps, a single lamp having a singlefilament, or a buzzer, or any other suitable indicator such as a coloredlamp can be used to provide an alarm indication without departing fromthe scope of the present invention.

FIG. 4 is a schematic diagram illustrating an example of the circuitryof the ground fault circuit interrupting device of FIG. 1 in accordancewith an embodiment of the present invention. In accordance with thisembodiment, the GFCI device 10 is provided with a latching mechanism 46,sensing circuit 48, solenoid 50, solenoid plunger 52, latching plate 54(See FIG. 8), reset pin 56 (See FIG. 8), locking plate 58, lockingspring 60, secondary contacts 62, neutral conductor 64, hot conductor66, a transformer arrangement 68 comprising sensing transformer 68A andground transformer 68B, and a control circuit 70.

GFCI device 10 is structured and arranged to prevent an initialmiswiring of the GFCI. That is, as described in more detail below, priorto shipping the device for use, the locking plate 58 is pressed downwardto engage a projection on the back of plunger 52 and makes contact withsecondary contacts 62 to thus close the secondary contacts 62. The resetbutton 34, when depressed, cannot engage with the latching plate 54 viathe reset pin 56 and through aperture 55 (See FIGS. 8–10) in thelatching plate 54. When the GFCI receptacle 10 is connected to the lineside, the secondary contacts power the solenoid 50, causing solenoidplunger 52 to release locking plate 58 and position latching plate 54 sothat the reset pin 56 can engage with the edge of the latching plate 54forming the opening 55 when the reset button 34 is depressed.

FIGS. 5–7 are perspective views illustrating examples of positions ofthe locking plate 54 in accordance with an embodiment of the presentinvention. In FIG. 5 the cover portion 14 of the housing 12 is removedto expose the internal housing 13 of the GFCI 10. The locking spring 60,secondary contacts 62, solenoid plunger 52 and solenoid 50 are shown.The locking spring 60 is in an extended or release position and is notexerting pressure.

In FIG. 6, the locking plate 58 is shown in a released or extendedposition. The locking spring 60 (See FIG. 5) holds the locking plate 58up, thus preventing aperture 59 of the locking plate 58 from engagingwith the projection 53 of the plunger 52 or from making contact with thesecondary contacts 62 and closing the secondary contacts 62.

In FIG. 7, the locking plate 58 is shown as being in the down positionand engaged with the projection 53 on the plunger 52 and, thus closingthe secondary contacts 62. That is, an aperture 59 in the locking plate58 interlocks with the projection 53 on the plunger 52 and holds thelocking plate 58 in a position in which the locking plate 58 makescontact with and closes the secondary contacts 62. When the reset button34 is depressed and the locking plate 58 is in a locked state, the resetpin 56 cannot engage with the latching plate 54 because the plunger 52positions the latching plate 54 such that the reset pin 56 passesthrough opening 55 freely. The locking plate 58 will remain in thisposition until the GFCI receptacle 10 is powered from the line side. Ascan be appreciated from the schematic in FIG. 4, the load terminals 37and 38 are electrically isolated from the remainder of the circuit whenthe latching mechanism 46 is in the open state as shown in FIG. 4.However, as is also shown, the secondary contacts 62, when closed by thelocking plate 58, provide a path which enables the solenoid to bepowered from the power source connected to the line terminals 39 and 40and move the plunger 52 in the direction of “A”, thereby removing theprojection 53 of the plunger 52 from the aperture 59 and releasing thelocking plate 58. Accordingly, the spring 60 raises the locking plate 58upward and out of contact with secondary contacts 62, thus opening thesecondary contacts 62.

FIGS. 8–10 are cross sectional views illustrating examples of positionsof the locking plate 58, a latching plate 54 and a reset pin 56 inaccordance with an embodiment of the present invention. In FIG. 8, thelocking plate 58 is shown as being engaged with the projection 53 of theplunger 52 via the aperture 59. The locking plate 58 makes contact withsecondary contacts 62, thus closing them. Locking spring 60 iscompressed and exerts pressure against the locking plate 58, but cannotmove locking plate 58 upwards because locking plate 58 is held in placeby projection 53. In addition, latching plate 54 is positioned toprevent the reset pin 56 from engaging with the latching plate 54. Thatis, the latching plate 54 is positioned to allow the reset pin 56 tofreely pass through the latching plate 54 when the reset button isdepressed without engaging with the latch plate 54.

In FIG. 9, the GFCI receptacle 10 is powered from the line side. Thesecondary contacts 62 which are closed, power the solenoid 50, whichdrives the plunger 52 forward in the direction of “A”. This releases theprojection of the plunger 52 from the aperture 59, and also pushes theplunger 52 against the latching plate 54 to position the opening 53slightly out of alignment with the reset pin 56. The locking spring 60urges the locking plate 58 upward, thus forcing the locking plate intoan extended or non-contacting position. The secondary contacts 62 openand remove power from the solenoid 50.

As shown in FIG. 10, the GFCI receptacle 10 is in a state of normaloperation. That is, the locking plate 58 and locking spring 60 are in anextended position, the secondary contacts are open, and the reset pin 56is able to engage with the edges of the latch plate 54 forming theaperture 53, thus allowing the upper shoulder 57 of the reset pin 56 tocontact and thus engage with the underside of latching plate 54 when thereset button is depressed. Although not shown specifically, the spring60 can thus urge the reset button upward along arrow “UP”, thus drawingthe latch plate 54 and latch block 63 upward. The latch block 63 thuscloses the contacts of latching mechanism 46 to thus provide electricalconnection between the line terminals 39 and 40, and their respectiveload terminals 37 and 38 and face terminals “hot face” and “neutralface”.

Referring now to FIG. 1 and the operation of the GFCI receptacle 10 in aground fault state. The GFCI receptacle 10 is disabled upon detection ofa current imbalance. Specifically, the sensing circuit 48 selectivelyplaces the solenoid 50 in a ground fault state in response to animbalance of current flow in the AC receptacle. While the solenoid 50 isshown here as being a solenoid, other devices such as piezoelectriccomponents and micro electromechanical systems (MEMS) may be used. Itcan also be seen that the latching mechanism 46 is connected to thesensing circuit 48 and is placed in series with a plurality ofconductive paths between opposing terminals of the receptacle.Specifically, the latching mechanism 46 breaks a plurality of conductivepaths leading from side line terminals 39 and 40 to side load terminals37 and 38 of the GFCI device 10 when the solenoid 16 is placed in theground fault state.

The latching mechanism 46 is structured such that plugins 18 and 20, theface receptacles, are isolated from the line terminals 39 and 40 and theload terminals 37 and 38. Thus if the GFCI 10 is miswired and/or in atripped position, plugins 18 and 20 will not be powered. A detaileddescription of the operation of latching mechanism 46 can be found inU.S. patent application Ser. No. 10/434,101, referenced above. Latchingmechanism 46 provides improved safety while maintaining a relatively lowlevel of complexity with regard to conventional approaches.

It should be noted that the sensing circuit 48 effectively defines animbalance of current flow as any difference in the amount of currentflowing in the candidate paths that rises above a predeterminedthreshold.

To better demonstrate the operation of latching mechanism 46, thesensing circuit 48 will now be described in greater detail. Generally,it can be seen that the sensing circuit 48 has a transformer arrangement68, a control circuit 70 and a test switch 30. The transformerarrangement 68 generates control signals in response to the imbalance ofcurrent flow, while the control circuit 70 is connected to thetransformer arrangement 68 and selectively generates a switching signalbased on the control signals. The test switch 30 is connected betweenthe line terminal 40 and the load terminal 37 such that the test switch30 enables manual generation of the imbalance of current flow.

Specifically, when the test switch 30 is closed (for example, manually,by an installer of the device), a circuit path is created from the loadterminal 38 to the line terminal 40, which creates an imbalance that isdetected by a first (or sense) transformer 68A. In an embodiment of theinvention, the first transformer 68A detects imbalances in the net fluxon the load side e.g. terminals 37 and 38 of the GFCI receptacle 10, andoperates in conjunction with the control circuit 70 to energize thesolenoid 50.

Detection of the imbalance condition by the first transformer 68A andthe control circuit 70 causes activation of the solenoid 50 such thatthe latching mechanism 46 is open as shown in FIG. 1. It can be furtherbe seen that a second (grounded neutral) transformer 68B is alsoprovided to allow the transformer arrangement 68 to measure the changein net flux between the first conductive path 64 and the secondconductive path 66.

It can be seen that the control circuit 70 preferably includes anamplifier and trip circuit 72, a full-wave bridge rectifier 74 and asilicon controlled rectifier (SCR) 76. The amplifier and trip circuit 72generate the switching signal, where the bridge rectifier 74 isconnected to the line side terminals 39 and 40. It can be seen that thebridge rectifier 74 provides power to the amplifier and trip circuit 72and that the SCR 76 selectively energizes the solenoid 50 based on theswitching signal. The control circuit 70 preferably includes thecomponents listed in the following table:

CAPACITOR C1 10 MIC OF AND, 16 VDC ALUM, ELECTROLYTIC CAPACITOR C2 3.3MIC, 16 VDC ALUM, ELECTROLYTIC CAPACITOR C3 .01 MIC, 50 VDC CERAMICCAPACITOR C4 .033 MIC, 25 VDC CERAMIC CAPACITOR C5 .01 MIC, 500 VDCCERAMIC CAPACITOR C6 .01 MIC, 50 VDC CERAMIC CAPACITOR C7 470 PIC, 50VDC CERAMIC DIODE D1 IN4004 DIODE D2 IN4004 DIODE D3 IN4004 DIODE D4IN4004 DIODE D5 IN4004 RESISTOR R1 15K OHM, ¼ W CARBON FILM RESISTOR R21.5 MED OHM, ¼ W METAL FILM RESISTOR R3 24K OHM, ½ W CARBON FILMRESISTOR R4 200 OHM, ¼ W CARBON FILM IC RV4145

The state of the latching mechanism 46 as shown in FIG. 4 indicates thatthe solenoid 50 has entered the ground fault state, due to depression ofthe test button 30 or due to an actual ground fault. However, when thesolenoid 50 is not in the ground fault state and the latching mechanism46 has been properly reset so that latching mechanism 46 is closed afirst and second path is created connecting the line terminals 39 and 40to the load terminals 37 and 38 providing power to a load when the GFCI10 is powered from the line side.

It is also important to note that when in the ground fault state, asshown in FIG. 1, an alternative current path is provided between theload terminal 37 and the line terminal 40. Thus, if the AC source isconnected to the line side of GFCI receptacle 10 and the test switch 30is closed, current flows from line side terminal 40, through resistorR1, to the load terminal 37. Thus, this current path will create animbalance in the transformer arrangement 68 resulting in the latchingmechanism 46 being open.

FIG. 11A is a schematic diagram illustrating an example of the groundfault circuit interrupting device of FIG. 3 in accordance with anotherembodiment of the present invention. The GFCI receptacle 11 is similarin operation to the GFCI device 10 discussed above except GFCIreceptacle 11 includes an alarm indicator 44, a test switch 30 havingprimary contacts TS1 and secondary contacts TS2. A detailed descriptionof the operation of the test switch can be found in U.S. patentapplication Ser. No. 10/032,064, filed on Dec. 31, 2001 entitled “GroundFault Circuit Interrupter (GFCI) With A Secondary Switch ContactProtection”, which is incorporated herein by reference.

When test switch 30 is pressed and closes primary test switch contactsTS1, an imbalance is created. The latching mechanism 46 opens and thealarm indicator 44 is extinguished and no longer provides a greencolored illumination. Since the latching mechanism 46 is open, thesubsequent closing of secondary test switch contacts TS2 by test switch30 has no affect on GFCI 11.

In contrast, if the closing of primary test switch contacts TS1 fails totrip the latching mechanism 46, secondary test switch contact TS2 causesa short circuit blowing the fuse F10 and extinguishing the alarmindicator 44 providing green illumination. However, the alarm indicator44 illuminates red. Diode DC10, resistor R11 and capacitor together actto flash alarm indicator 44. The flashing alarm indicator 44 indicatesto a user that GFCI 11 is not providing ground fault protection and isonly operating as an unprotected receptacle and not as a GFCI. Alarmindicator 44 will only flash red when the latching mechanism fails totrip. Thus, the alarm indicator can also serve to provide an indicationof a defective solenoid 50, or any other component of the GFCI that aidsin tripping the latching mechanism 46.

Embodiments of the present invention will now be described withreference to FIGS. 11B and 11C. Both FIGS. 11B and 11C apply tosituations where a single LED is used.

FIG. 11B is a schematic diagram illustrating an example of amodification to the circuitry of the ground fault circuit interruptingdevice of FIG. 11A in accordance with an embodiment of the presentinvention. Specifically, GFCI device 200 operates in substantially thefollowing manner. If the GFCI device 200 is miswired from the load side,correctly wired from the line side and the latching mechanism 46 isopen, or correctly wired from the line side and the latching mechanism46 is closed, alarm indicator 244 is in an off state where noillumination is provided. Since conductive path 202 which comprises fuseF10 and conductor 207 offers less resistance than conductive path 204which comprises resistors R10, R11, capacitor C10, diodes D10, and alarmindicator 244, current passes through conductive path 202 rather thanconductive path 204. Thus, alarm indicator 244 does not illuminate undernormal conditions.

It should be appreciated by those skilled in the art that although alarmindicator 244 in this example is a red LED, any color LED, e.g., green,yellow, orange, and the like can be used without departing from thescope of the present invention. Furthermore, an audible device can beused to indicate an alarm condition. Visual indications and audibleindication can be used together or separately to practice an embodimentof the present invention.

In terms of test switch contacts TS1 and TS2, when test switch 30 ispressed and closes primary test switch contacts TS1, an imbalance iscreated. The latching mechanism 46 then opens. Since the latchingmechanism 46 is open, the subsequent closing of secondary test switchcontacts TS2 by test switch 30 has no affect on GFCI device 200.

However, if the closing of primary test switch contacts TS1 fails totrip the latching mechanism 46, secondary test switch contact TS2 causesa short circuit blowing the fuse F10, and creating an open in conductivepath 202. Current now flows through conductive path 204, which energizesalarm indicator 244, which is preferably a red LED as discussed above.Diode DC10, resistor R11 and capacitor C10 together act to flash alarmindicator 244. The flashing alarm indicator 244 indicates to a user thatGFCI device 200 is not providing ground fault protection and is onlyoperating as an unprotected receptacle and not as a GFCI. Alarmindicator 244 will only flash red when the latching mechanism fails totrip. Thus, the alarm indicator can also serve to provide an indicationof a defective solenoid 50, or any other component of the GFCI that aidsin tripping the latching mechanism 46.

FIG. 11C is a schematic diagram illustrating another example of amodification of the circuitry of the ground fault circuit interruptingdevice of FIG. 11A in accordance with an embodiment of the presentinvention. Specifically, GFCI device 201 operates in substantially thefollowing manner. If the GFCI device 201 is miswired from the load sideor GFCI device 201 is correctly wired from the line side and thelatching mechanism 46 is open, alarm indicator 246 will not illuminatesince latching mechanism 46 is normally open and breaks any conductivepath that provides current to illuminate alarm indicator 246. When GFCIdevice 201 is correctly wired from the line side and the latchingmechanism 46 is closed, alarm indicator 246 is in an on state whereillumination is provided.

In terms of test switch contacts TS1 and TS2, when test switch 30 ispressed and closes primary test switch contacts TS1, an imbalance iscreated. The latching mechanism 46 opens and the alarm indicator 246 isextinguished and no longer provides a green colored illumination. Sincethe latching mechanism 46 is open, the subsequent closing of secondarytest switch contacts TS2 by test switch 30 has no affect on GFCI 11.

On the other hand, if the closing of primary test switch contacts TS1fails to trip the latching mechanism 46, secondary test switch contactTS2 causes a short circuit blowing the fuse F10, and creating an open inconductive path 206. This extinguishes alarm indicator 246, whichprovides an indication to a user that there is a problem with GFCIdevice 201.

It should be appreciated by those skilled in the art, that the presentinvention can be modified to have alarm indicator 246 flash rather thanbe extinguished without departing from the scope of the presentinvention. In addition, an audible alarm can be added to provide anindication that latching mechanism 46 failed to open under test. Theaudible alarm can be provided either with or without a visual indicationin order to practice an embodiment of the present invention.Furthermore, alarm indicator 246 is not limited to any particular color.For example, LEDs or lamps that display white, yellow, blue, orangecolors and the like can be used to practice embodiments of the presentinvention.

FIG. 12 is a perspective view of an example of a ground fault circuitinterrupting (GFCI) device in accordance with another embodiment of thepresent invention. The GFCI 115 does not contain isolated face terminalsand performs ground fault detection in a manner known to those skilledin the art and will be discussed with reference to its novelty. The GFCI115 includes latching plate 153 (See FIG. 13), secondary contacts 162and a locking plate 157. Latching plate 153 is structured and arrangedso that a portion of the latching plate passes through a plunger end 151(See FIG. 13). The portion of the latching plate 153 passing through theplunger end 151 has a curved end. The curved end of the latching plate153 allows the plunger end 151 to move the latching plate 153 laterallyin the direction of “A” and “B”. Proximate its center, latching plate153 has an aperture 154 to allow reset pin 156 to engage with thelatching plate 153 when the reset button 134 is depressed. In a resetprevention state, the latching plate 153 is positioned such that thereset pin 156 freely passes through the latching plate 153.

Locking plate 157 is used to place the GFCI 115 in a reset preventionstate. The locking plate can be a pin type device, which is insertedthrough the aperture 142 during the manufacturing process between theplunger 151 and the secondary contacts 162, thus closing the secondarycontacts 162. When the GFCI 115 is powered from the load side, there isno power to the solenoid 150. Therefore, the GFCI 115 remains in a resetprevention state because upper shoulder 149 of the reset pin 156 cannotlatch with the bottom surface of the latching plate 153 and reset theGFCI 115. When the GFCI 115 is powered from the line side, the solenoidis powered and moves the plunger in the direction of “B” slightlymisaligning the aperture 154 in the latching plate 153 with the resetpin 156, thus allowing the upper shoulder 149 of reset pin 156 tocontact the lower surface of latching plate 153, and thus pull latchplate 153 and latch block 159 upward to close the contacts of latchingmechanism 178 in a manner similar to that discussed with regard to latchplate 54 and latch block 63. The locking plate 157 falls and opens thesecondary contacts 162, removing power from the solenoid 150.

This embodiment of the invention will now be discussed with reference toFIG. 13–16 which are views illustrating examples of positions of alocking plate in the GFCI of FIG. 12 in accordance with an embodiment ofthe present invention. In FIG. 13, secondary contacts 162 are open andthe locking plate 157 is being inserted into the GFCI 115 via theaperture 142.

In FIG. 14, the locking plate 157 comprising a pin type device isinserted between the plunger 151 and the secondary contacts 162, thusclosing the secondary contacts 162 and allowing the secondary contacts162 to power the solenoid 150 if the GFCI 115 is wired from the lineside. The latching plate 153, however, is positioned to allow the resetpin 156 to freely pass through the aperture 154 and thus not engage withthe latching plate 153 unless the GFCI 115 is connected to the line sidein a manner similar to that discussed above with regard to FIGS. 4–10.

In FIG. 15, the GFCI 115 has been wired to the line side and the plunger151 moves in the direction of “B” to release the locking plate 157. INFIG. 16, the plunger 151 moves in the direction of “A” allowing anaperture in the latch plate 153 to be slightly, misaligned with thereset pin 156 as shown in FIG. 16.

FIGS. 17A and 17B are cross sectional views illustrating examples ofpositions of an initial reset prevention arrangement that can be usedwith a GFCI in accordance with another embodiment of the presentinvention. For conciseness, the details of the reset button, and resetpin are not repeated here. In FIG. 17, the locking plate 182 comprises avertical member 182A connected to a horizontal member 182B proximate thecenter of the horizontal member 182B. A locking spring 180 is disposedbetween a portion of the inner housing 113 and an end of the horizontalmember 182B. The locking spring 180 exerts force on the horizontalmember 182B in the direction of “C”. An opposing end of the horizontalmember 182B makes contact with secondary contacts 178 in order to closethe secondary contacts 178. The locking plate 182 is shown in anon-initial reset prevention state. That is, the plunger end 151 doesnot retain the vertical member 182A of the locking plate 182 in aposition in which the horizontal member 182B closes the secondarycontacts 178 by making contact with the secondary contacts 178.

Referring now to FIG. 17B, the plunger end 151 is shown retaining thevertical member 182A of the locking plate 182 which enables thehorizontal member 182B to close the secondary contacts 178. The latchplate 153 is positioned so that the end of the reset pin (not shown) canfreely pass through the opening 154 as discussed above, to preventresetting. As also discussed above, the locking spring 180 is compressedby an end of the vertical member 182 which exerts force in the directionof “C”. When the GFCI is powered from the line side, the secondarycontacts 178 power the solenoid 150 which results in the plunger 151moving in the direction of “A”, thus releasing the locking plate 182.Substantially simultaneously, the spring 180 exerts force on thehorizontal member 182B to propel the horizontal member 182B in thedirection of “C” and open the secondary contacts 178.

FIGS. 18A and 18B are cross sectional views illustrating examples ofpositions of a another initial reset prevention arrangement that can beused with a GFCI in accordance with an embodiment of the presentinvention. Referring to 18B, the solenoid 150 includes a plunger 184having a vertical member 184A, a horizontal member 184B and an aperture184C. The vertical member 184A is connected to the solenoid 150 and to alatching plate 186, which is similar to latching plate 153 discussedabove. The horizontal member 184B is connected to the vertical member184A. In an initial reset prevention state, the pin 191 of locking plate190 is aligned with and passes through aperture 184C engages with theupper surface of horizontal member 184B, and thus closes the secondarycontacts 192. In this position, an aperture 187 in the latching plate186 is substantially aligned with a reset pin (not shown) to thus allowthe reset pin to pass through the aperture 187. Thus, the reset pincannot latch with the latching plate 186 and close the latchingmechanism (not shown) to reset. The locking spring 188 is compressed andexerts force on the locking plate 190 in the direction of “C”. However,the locking spring 188 cannot pull the locking plate 190 out of theaperture 184C unless the GFCI is powered from the line side.

Referring now to FIG. 18A, the GFCI has been wired to the line side. Thesecondary contacts 192 power the solenoid 150 moving the plunger 184 inthe direction of “B”. This movement releases the locking plate fromaperture 184C. The locking spring 180 propels the locking plate 190 awayfrom the aperture 184C and secondary contacts 192 to a position of restas shown. The release of the locking plate 190 moves the latching plate186 to slightly misalign the aperture 187 in the latching plate 186 withthe reset pin. Thus, the reset pin can engage the latching plate 186 andreset the contacts to a closed state in a manner similar to thatdiscussed above.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention canbe described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, specification and following claims.

1. A protective device having source and load terminals between aconductive path and face terminals, the protective device comprising: alatching mechanism, adapted to be operable between a first state inwhich said latching mechanism permits electrical contact between saidsource terminals and said load terminals and a second state in whichsaid contact is broken; an alarm indicator, adapted to provide anindication that said protection device is not providing ground faultprotection; and a fuse, adapted to blow when said latching mechanismfails to open during a manual test of the protection device, said alarmindicator providing said indication in response to said fuse blowing. 2.A protection device according to claim 1, wherein said alarm indicatoris a Light Emitting Diode (LED).
 3. A protection device according toclaim 2, wherein the LED flashes to indicate the device is not providingground fault protection.
 4. A protection device according to claim 2,wherein the LED extinguishes to indicate the device is not providingground fault protection.
 5. A protection device according to claim 2,wherein the LED comprises a red LED.
 6. A protection device according toclaim 1, further comprising: a sensing circuit, adapted to selectivelyplace the latching mechanism in said second state upon detection of aground fault condition to electrically isolate said face terminals fromsaid source and load terminals.
 7. A protective device according toclaim 1, wherein said protective device includes a ground fault circuitinterrupter (GFCI).
 8. A protective device according to claim 1, whereinsaid source terminals and load terminals are adapted to connect to apower source.
 9. A protective device according to claim 1, wherein saidlatching mechanism comprises: an electromechanical device, adapted toplace said latching mechanism in one of said first and second states; afirst transformer, adapted to detect a current imbalance in saidconductive path; and a second transformer, adapted to detect an amountof the current imbalance in said conductive path.
 10. A protectivedevice according to claim 9, wherein said electromechanical devicecomprises a solenoid.
 11. A protective device according to claim 1,wherein said first state comprises a closed condition and said secondstate comprises an open condition.
 12. A protective device according toclaim 9, wherein when said latching mechanism is in said second statesaid face terminals are isolated from said power source if said powersource is connected to either said load terminals or said sourceterminals.
 13. A protective device according to claim 1, wherein saidface terminals include contacts separate from said conductive path andsaid source and load terminals.
 14. A protective device according toclaim 1, wherein said conductive path comprises: a neutral conductor,adapted to connect said source and load terminals; and a hot conductor,adapted to connect said source and load terminals.
 15. A method ofproviding a protection device that indicates a lack of ground faultprotection being provided by said protection device, comprising:providing a latching mechanism for operating between a first state inwhich said latching mechanism permits electrical contact between sourceload terminals and load terminals and a second state in which saidcontact is broken; blowing a fuse when said latching mechanism fails toopen during a manual test of the protection device; and energizing analarm indicator when said fuse blows to indicate that said protectiondevice is not providing ground fault protection.
 16. A method accordingto claim 15, wherein said alarm indicator is a Light Emitting Diode(LED).
 17. A method according to claim 16, wherein the LED flashes toindicate the device is not providing ground fault protection.
 18. Amethod according to claim 16, wherein the LED extinguishes to indicatethe device is not providing ground fault protection.
 19. A methodaccording to claim 16, wherein the LED comprises a red LED.
 20. A methodaccording to claim 15, further comprising: providing a sensing circuitfor selectively placing the latching mechanism in said second state upondetection of a ground fault condition to electrically isolate faceterminals from said source and load terminals.
 21. A method according toclaim 15, wherein said protective device comprises a ground faultcircuit interrupter (GFCI).